An Extended Characterization of European Advanced$rm Nb_3rm Sn$Strands for ITER

Within the framework of ITER-related projects, new tasks have been recently launched by EFDA CSU Garching (European Fusion Development Agreement Close Support Unit Garching), for the definition and production on industrial scale of advanced
$ Nb_3 Sn$
strands, to be used in the manufacturing of the ITER high field CS and TF magnets. We performed an extended characterization of the advanced
$ Nb_3 Sn$
strands coming from different European companies, in terms of strand layout (diameter, thickness of
$ Cr$
coating,
$ Cu$
:non-
$ Cu$
ratio), critical transport current, RRR, and hysteresis losses. The results of the measurement campaign show that the upgraded strands meet the latest ITER requirements, with an overall critical transport current of at least 200 A (at 12 T, 4.2 K), equivalent to a non-
$ Cu$
Jc of about 800
$ A/mm^2$
, a
$ Cu$
:non-
$ Cu$
ratio of about 1, a strand diameter of 0.81 mm, and with non-
$ Cu$
hysteresis losses limited to less than 1000
$ kJ/m^3$
on a
$pm$
3 T field cycle at 4.2 K.